1. Field of the Invention
This invention generally relates to energy management and, more particularly, to a system and method for representing energy consumption as interdependent multi-dimensional energy characteristics.
2. Description of the Related Art
One of the goals of a home energy management system (HEMS) is to manage energy in the most effective way to satisfy the residents' desires. One issue in attaining this goal is to determine the residents' desires. Some HEMSs assume that residents want to minimize cost of energy within preset bounds. Other systems offer a set of goals, such as cost and comfort, on which the user selects a preference. The preference level can be set as a number between a minimum and a maximum value, such as 0 to 100, or may be set as one of a set of fixed values, such as low, medium, and high.
There are control systems that optimize the system performance characteristics against a set of input weights on those characteristics. For example a climate control system may optimize the HVAC system output for temperature, or economy, or humidity, or turnover, or any number of measures of air quality. Control systems may have input settings provided by the operator to tell the system how to tradeoff competing characteristics. The tradeoff input is often supplied in the form of a number set between a minimum and maximum value (say 0 to 100) to indicate the relative weight to put on the characteristic. The weight on each of the characteristics is input to the control system by such means as a numerical input, a dial setting, or any method that can be transformed into a value between the minimum and maximum.
However, even if a user is given the option of managing their home energy use using a combination of considerations, it is often difficult for the uninformed to select appropriate operating limits for appliances. This is especially true when the user needs to pick operating limits for somewhat abstract notions such as “cost savings”, “ecology mode”, and “comfort mode”.
For example, when the outside temperature is more than 70 degrees, a temperature up to 5 degrees over the setpoint, and 10 degrees below the setpoint may be tolerated by a user. When the outside temperature is less than 60 degrees, the user can likely tolerate up to 5 degrees over or under the setpoint. These functions are difficult to implement. Further, appliances that could delay their work and function by a given time can eliminate much of the inconvenience of timed execution.
The industry commonly uses price as a way of controlling time of use. Some utilities have Time of Day pricing (TOD), some use Dynamic pricing (which works well with automated homes that can delay usage) where the price changes every 15 minutes to match wholesale prices (with some limits). Other utilities implement emergency notices called Demand Response (DR) and they give incentives for reducing electricity usage for short periods (maybe $1.50 for reducing usage for 2 hours).
Varying prices and incentives are negative because they favor the consumers who can afford the automation, and they may surprise consumers with unexpected high bills. Because of the negative aspects of price control and incentive programs combined with the slow pace of utility negotiations with their regulators, most of the US residential customers have the same price of electricity throughout the day regardless of the instantaneous wholesale price of electricity.
Because electricity cost does not vary as much as the real instantaneous cost to produce the electricity, shifting loads to when electricity is cheapest to produce does not give the user a direct cost benefit, but in general, it would lower the price of electricity for the community as a whole. Hence, ecological-based energy management may lower the overall cost of electricity by utilizing the equipment more efficiently and postponing the building of more generation and transmission facilities. That is, greater use of the ecology mode could either minimize the cost of electricity production, or minimize the environmental damage of electricity production.
Many times, reducing the cost of electricity also reduces the environmental impact. For example, postponing building more plants and transmission lines by using what is available avoids the impact of the extra resources. However, renewable resources are much more expensive than coal plants, so electricity cost can be opposite to environmental costs. As more renewable sources become available, the ecology mode should ensure that these sources are fully utilized. When renewables become dominant, then the ecology mode should constantly shift usage to match renewable energy availability.
It would be advantageous if a home energy user could be given a visually intuitive control method that permitted control over a plurality of interdependent energy considerations. It would be advantageous if a multi-dimensional energy space of energy characteristics could be represented as two-dimensional polygonal figure on a graphic display.